The present invention relates generally to fastening devices and more particularly to fastening devices utilizing wire bristles to retain a bolt threaded therethrough.
The use of nuts and bolts as fasten devices is centuries old. An ordinary nut descends down the shaft of a bolt only along the path where the threads of the nut interlock with the threads of the bolt. When an external force (encountered for example at the surface of the fixed-member being bolted into) impedes the ordinary nut's smooth rotation, the nut tightens, descends at a slower pace, and its rotation ultimately stops.
During initial threading an ordinary nut can begin descent down the shaft of a bolt only when its threads are aligned with those of the bolt (within a half-thread). A bolt can thread through an ordinary nut only along the path where their threads interlock.
External threading resistance is typically met when a nut meets the under-surface of a fixed member to which the remote member is being fastened, when a force impinges on the bolt itself, or when a nut meets either a bolt-thread ending or the head of a bolt. Whenever it is met, an ordinary nut reacts to threading resistance by creating tension in the bolt and tightening. The nut descends at a slower pace and eventually stops rotating (unless such a force is applied as to strip the fixed threads).
While these characteristics enable an ordinary nut to perform the fastening function for which it was designed, there are applications where a different type of nut would be beneficial. In certain situations a nut that does not fasten but performs other functions such as bolt guiding or alignment, bolt holding, or force absorbing would be useful.
An additional application of fasteners is for remote assembly of heavy plant equipment in contaminated areas. Upon disassembly of equipment, conventional capture devices provide "capture" of the fastening bolt; the bolt used for fastening is held in place in a remote section and is aligned perpendicular to the remote member's surface (hereafter "vertically"), so that re-fastening to the fixed section is easy when assembly is needed again. Internal threads in the remote member portion of the device in combination with a light-action spring perform the "capture" function. As the bolt is removed from the fixed member, the light-action spring lifts the bolt up and the bolt threads meet the threads inside the remote member portion of the device. The internal remote member threads hold the bolt in place and ensure that it is captured, aligned vertically and ready for refastening.
However, the conventional remote fastening "capture" devices are unnecessarily complicated and costly. Rather than having a straight cylindrical hole through the remote member portion of the device, it has a hole with three different diameters; a wide diameter where the spring sits, a narrow diameter where the internal threads are bored, and another wide diameter. Threads inside the hole are difficult to make and must be bored with the utmost precision. Thus a simpler design would be desirable.
An additional use of fasteners is in load-test rigs used for determining the duty rating of cranes in contaminated areas. One such apparatus consists of twenty-five one-ton steel plates stacked on top of each other. A lifter beam fits through holes at the center of the stacked plates and for each lift, one bolt pin slides under a particular plate depending on the desired load and interlocks with the plate beam.
While use of threaded pins enables precise insertion and easy remote control, there is a problem with the force exerted on the pins. The pins are rotated, and thus inserted or withdrawn using an impact wrench on the head of the bolt. When rotated, the impact wrench exerts 550 foot-pound of torque which can result in tension or compression loads of 100,000 pounds. When an ordinary nut is installed under the plates, the nuts either have to be manufactured to such high standards (along with the bolt threads) as to withstand the force exerted by the impact wrench, or there has to be very precise control over the wrench's rotation. In either case, this is expensive.